Inductive displacement sensors are used for displacement measurement in motor vehicles, which are made up of an induction coil having two terminals and a soft magnetic armature which is displaceable in the induction coil. Thus, the inductance of the coil is a function of the setting of the armature relative to the coil, so that such sensors are suitable for displacement measurement. Such sensors are frequently used in automotive technology, since they are cost-effective to manufacture and are very robust to environmental influences, such as temperature change, stresses from shaking or soiling. Compared to other sensors, such as potentiometers, Hall sensors or optical sensors, the signal processing may be slightly more costly, and problems come about at greater requirements on the stability with regard to temperature-dependent signal aliasing.
The evaluation of such inductive sensors up to now has been made by applying a current pulse or a voltage pulse to the sensor, and by concluding what the current inductivity is with the aid of the step response. The semiconductors and capacitors used for the control of the sensors in many circuits demonstrate a temperature-dependent error, which deteriorates the sensor signal. Also, voltage peaks occur during the switching off of the sensor, which have to be limited using additional anti-surge diodes, in order to avoid damage at other circuit elements. Since the copper line of the sensor coils has a temperature-dependent Ohmic resistance, at higher demands on the signal stability, this Ohmic resistance, and therewith indirectly the temperature of the sensor has to be recorded and drawn upon for error correction. Therefore, in practice, inductive displacement sensors are used only for measurements having low resolution and stability.